it all depends on what you are looking to do, if you are only creating one blog then I would say word press for sure is the best, lots more to word press and lots of developers developing many modules for free. You can use this to assist in your blog getting a good ranking, however word press is a little harder to learn it is in my opinion the better of the 2.
If you want to create more than one blog or not to bothered about revenue then i would suggest blogger as its a little friendlier to use.
I would do more research before you start so you are sure you have chosen the correct one, i hope this information is of some help to you.
Mark Leroy, Kilwinning, CA